1. Field of the Invention
The present invention relates to a bearing structure for a flat motor for use as the drive motor for magnetic disk drives or cooling fans mounted in office automation equipment.
2. Description of the Prior Art
Fans are mounted in the chassis walls of computers and peripheral equipment which contain a large number of heat emitting electronic circuits in order to expel the hot air from inside the chassis and keep the internal temperature low. Furthermore, electronic circuits such as CPUs which generate large amounts of heat may be fitted with their own cooling fans which blow air across cooling fins to dissipate the heat.
The prior art will not be described with reference to FIG. 20, which is a sectional diagram showing a conventional fan as described in U.S. Pat. No. 4,620,139. This fan 100 has a cylindrical bearing holder 51 in the center of the cup-shaped motor housing 50. Pluralities of supports 53 are positioned in space 52 on the inside of motor housing 50. Printed wiring circuit board 55 is arranged on top of stator yoke plate 54 which rests on the shoulder of bearing holder 51 and on the top of supports 53. A plurality of stator coils 56 are fixed to the top surface of printed wiring circuit board 55.
Two ball bearings 57, 58 are mounted at the upper and lower inside edges of bearing holder 51, and rotating shaft 59 is held in place by the inner races of these bearings. A cup-shaped boss 60 projects inwardly from the center of rotor 62, to the circumference of which are attached fan blades 61. The tip of said rotational shaft 59 is inserted into and fixed by said boss 60 allowing rotational shaft 59 and rotor 62 to rotate freely in relation to the motor housing 50. On the inside of rotor 2, rotor magnet 63 is arranged in opposition to stator coil 56 which is mounted on said printed wiring circuit board 55. The number 64 refers to the rotor yoke mounted on the reverse side of rotor magnet 63.
In the conventional flat fan motor described above, rotor 62 is made to rotate by the pulling action on rotor magnets 63 of the magnetic field generated in rotor coil 56 by the electronic components on printed wiring board 55. In order to allow stable rotation for said rotor 62 and to suppress vibration in the radial and axial directions, rotating shaft 59 is rotatively supported by two ball bearings 57, 58 arranged with a gap between them.
In response to the trend for various kinds of office automation equipment to be made smaller and thinner, there is a demand for smaller and thinner fans. Conventional motors such as that described above, in which 2 bearings are arranged with a gap between them in order to provide rotative support, have a structure which prevents the motor from being made smaller and thinner, and in addition they employ 2 high-priced ball bearings.
The present invention sets out to overcome the drawbacks of the conventional thin fan described above, with the objective of helping to make office automation equipment more compact and thinner. The new type of thin fan bearing structure provided by the present invention also allows the cost of such motors to be reduced.
In order to achieve the objectives described above, the present invention provides a bearing structure for a flat motor, having a rotor provided with permanent magnets which is rotatively supported by the bearing structure mounted on a casing and by a stator structure mounted on the casing, in which the rotating magnetic field generated by the stator structure in opposition to said permanent magnets causes the rotor to rotate; wherein either the outer race or the inner race of a compound bearing structure comprising one single row ball bearing and a cylindrical bearing, is fixed to the bearing structure mounted on said casing, while the other race is fixed to said rotor; the structure of said compound bearing comprising an outer race and an inner race, each fixed to opposing bearing portions and separated by a gap; a ball, which fits into ball grooves cut in the opposing surfaces of said inner and outer races which hold it so that it can roll freely; and a friction bearing, formed in a cylindrical shape and positioned on one side of the ball, and possibly also on the outer race and/or inner race; one face of said friction bearing being attached to either the inner or the outer face of one of the opposing bearing portions, the other face of said friction bearing forming a gap in opposition to the other opposing bearing portion, said gap restricting the inclination of the outer race and the inner race to within the specified permissible value.
Another present invention provides a bearing structure for a flat motor, having a rotor provided with permanent magnets which is rotatively supported by the bearing structure mounted on a casing and by a stator structure mounted on the casing, in which the rotating magnetic field generated by the stator structure in opposition to said permanent magnets causes the rotor to rotate; wherein either the outer race or the inner race of a compound bearing structure comprising one single row ball bearing and a cylindrical hearing, is fixed to the bearing structure mounted on said casing, while the other race is fixed to said rotor, the structure of said compound bearing comprising an outer race and an inner race, each fixed to opposing bearing portions and separated by a gap; a ball, which fits into ball grooves cut in the opposing surfaces of said inner and outer races which hold it so that it can roll freely; and a friction bearing, formed in a cylindrical shape and positioned on one side of the ball, and possibly also on the outer race and/or inner race; the outer face of said friction bearing being attached to a bearing portion and the inner face of said friction bearing being attached to the opposing bearing portion, the two faces forming a gap, said gap restricting the inclination of the outer race and the inner race to within the specified permissible value.
Still another present invention provides a bearing structure for a flat motor, having a rotor provided with permanent magnets which is rotatively supported by the bearing structure mounted on a casing and by a stator structure mounted on the casing, in which the rotating magnetic field generated by the stator structure in opposition to said permanent magnets causes the rotor to rotate; wherein either the outer race or the inner race of a compound bearing structure comprising one single row ball bearing and a cylindrical bearing, is fixed to the bearing structure mounted on said casing, while the other race is fixed to said rotor; the structure of said compound bearing comprising an outer race and an inner race, each fixed to opposing bearing portions and separated by a gap; a ball, which fits into ball grooves cut in the opposing surfaces of said inner and outer races which hold it so that it can roll freely; and a friction bearing, formed in a cylindrical shape and positioned on one side of the ball, and possibly also on the outer race and/or inner race; the inner face of said friction bearing being attached to a bearing portion and the outer face of said friction bearing being attached to the opposing bearing portion, the two faces forming a gap, said gap restricting the inclination of the outer race and the inner race to within the specified permissible value.
Further present invention provides a bearing structure for a flat motor, having a rotor provided with permanent magnets which is rotatively supported by the bearing structure mounted on a casing and by a stator structure mounted on the casing, in which the rotating magnetic field generated by the stator structure in opposition to said permanent magnets causes the rotor to rotate; wherein either the outer race or the inner race of a compound bearing structure comprising one single row ball bearing and a cylindrical bearing, is fixed to the bearing structure mounted on said casing, while the other race is fixed to said rotor; the structure of said compound bearing comprising an outer race and an inner race, each fixed to opposing bearing portions and separated by a gap; a ball, which fits into ball grooves cut in the center part of the opposing surfaces of said inner and outer races which hold it so that it can roll freely; and a friction bearing, formed in a cylindrical shape and positioned on both sides of the ball, and possibly also on the outer race and/or inner race; the outer face of said friction bearing being attached to a bearing portion and the inner face of said friction bearing being attached to one of the opposing bearing portions, the two faces forming a gap, said gap restricting the inclination of the outer race and the inner race to within the specified permissible value.
Further present invention provides a bearing structure for a flat motor, having a rotor provided with permanent magnets which is rotatively supported by the bearing structure mounted on a casing and by a stator structure mounted on the casing, in which the rotating magnetic field generated by the stator structure in opposition to said permanent magnets causes the rotor to rotate; wherein either the outer race or the inner race of a compound bearing structure comprising one single row ball bearing and a cylindrical bearing, is fixed to the bearing structure mounted on said casing, while the other race is fixed to said rotor; the structure of said compound bearing comprising an outer race and an inner race, each fixed to opposing bearing portions and separated by a gap; a ball, which fits into ball grooves cut in the center part of the opposing surfaces of said inner and outer races which hold it so that it can roll freely; and a friction bearing, formed in a cylindrical shape and positioned on both sides of the ball, and possibly also on the outer race and/or inner race; the inner face of said friction bearing being attached to a bearing portion and the outer face of said friction bearing being attached to one of the opposing bearing portions, the two faces forming a gap, said gap restricting the inclination of the outer race and the inner race to within the specified permissible value.